A BROAD-BRUSH APPROACH TO THE SELECTION OF GENERAL-PURPOSE CUTTING-TOOL GEOMETRY FOR MAXIMUM TOOL LIFE

This paper develops a ''broad-brush'' approach towards the selection o f the geometry of general purpose cutting tools for maximum tool life in the absence of a priori knowledge concerning the specific cutting c onditions at which the tools might be used. The large number of indepe ndent tool angles involved are combined into two independent non-dimen sional factors. The first is the mechanical stress intensity factor, < (sigma)over bar>(r), which determines the tool's relative susceptibili ties towards fracture and wear in the vicinity of the primary cutting edge. The optimum magnitude of this factor, (<(sigma)over bar>(r))(opt ), can be determined from the mechanical properties of the tool and wo rk materials. The second is the cooling power factor, C-g, which accou nts for the ability of the tool wedge to dissipate cutting heat. A sem i-empirical method is then used to integrate the two factors into one single variable which is shown to correlate well with experimental too l life magnitudes in turning and drilling. Finally, the approach is us ed to modify the corner geometry of standard drills with a view to min imising corner wear. The modification has enabled an improvement of dr ill corner life of the order of 400%. (C) 1997 Elsevier Science Ltd.